1. Field of the Invention
The present invention relates to a movement vector detection device, and, more particularly to a movement vector detection device for use in an optical imaging apparatus such as a TV camera, an electronic camera, a video camera, or an industrial image measurement meter. In particular, the present invention relates to a movement vector detection device for use in an optical imaging apparatus possessing a vibration isolation function and a tracking function.
2. Related Background Art
A method of detecting a movement vector by processing an image signal is exemplified by a time spatial inclination method disclosed in Japanese Patent Publication No. 60-46878 and U.S. Pat. No. 3,890,462. Letting the image displacement amount in the direction x be .alpha. and the image displacement amount in the direction y be .beta., .alpha. and B are calculated from the following equations in accordance with the former method: EQU .alpha.={.SIGMA..sub.B g.sub.y '.sup.2 (.SIGMA..sub.B g.sub.x 'd)-(.SIGMA..sub.B g.sub.x 'g.sub.y ') (.SIGMA..sub.B g.sub.y 'd)}/{.SIGMA..sub.B g.sub.x '.sup.2 .SIGMA..sub.B g.sub.y '.sup.2 -(.SIGMA..sub.B g.sub.x 'g.sub.y ').sup.2 } EQU .beta.={.SIGMA..sub.B g.sub.x '.sup.2 (.SIGMA..sub.B g.sub.y 'd)-(.SIGMA..sub.B g.sub.x 'g.sub.y ') (.SIGMA..sub.B g.sub.x 'd)} /{.SIGMA..sub.B g.sub.x '.sup.2 .SIGMA..sub.B g.sub.y '.sup.2 -(.SIGMA..sub.B g.sub.x 'g.sub.y ').sup.2 } (1)
In accordance with the latter method, they can be calculated by the following equations: EQU .alpha.=.SIGMA..sub.B d.sign(g.sub.x ')/.SIGMA..sub.B .vertline.g.sub.x '.vertline. EQU .beta.=.SIGMA..sub.B d.sign(g.sub.y ')/.SIGMA..sub.B .vertline.g.sub.y '.vertline. (2)
where d is the density (level) difference at the same position between the images which are sequentially continued in time, that is, the time inclination values, g.sub.x ' and g.sub.y ' are respectively spatial inclination .differential.g(x,y)/.differential.x in the x direction and spatial inclination .differential.g(x,y)/.differential.y in the y direction when the image is expressed by g, .SIGMA..sub.B means the sum calculation within a block which is a unit calculation region consisting of a plurality of pixels and sign ( ) is a function for transmitting the sign of g.sub.x ' and g.sub.y '.
Although the movement vector calculation by using Equation (1) has been used in accordance with the conventional inclination method, Equation (2) has attracted attention in actual time image processing in which high speed calculations are required.
However, a problem arises in Equation (2) in that the accuracy excessively deteriorates when .SIGMA..sub.B g.sub.x 'g.sub.y ' is a large value because Equation (2) is obtained by simplifying Equation (1) in such a manner that the term .SIGMA..sub.B g.sub.x 'g.sub.y ' of Equation (1 ) is approximated by 0.